The present invention relates to a high molecular weight norbornene-based polymer having a specified structure which is excellent in properties such as mechanical strength, heat resistance and transparency, a process for efficiently producing said polymer, a film made of said polymer which is excellent in heat resistance and transparency, and a process for efficiently producing said film.
It is known that radical polymerization, cationic polymerization, polymerization using a Ziegler-type catalyst or polymerization using a metathesis catalyst of 2-norbornene or its derivatives results in polymers.
In polymerization of 2-norbornene using a catalyst such as SnR.sub.4 /WCl.sub.5 or ReCl.sub.5, ring opening polymerization proceeds, resulting in formation of a rubber-like polymer having the following structural formula: ##STR3## (Norman G. Gaylord et al., J. Macromol. Sci-Chem., A 11 (5) 1053 (1977)). When TiCl.sub.4 /Et.sub.2 AlCl or Pd(C.sub.6 H.sub.5 CN).sub.2 Cl.sub.2 is used as a catalyst, vinylene-type polymerization proceeds, resulting in formation of a polymer having the following structural ##STR4## (U.S. Pat. No. 3,330,815).
However, in the case of the above Ticl.sub.4 /Et.sub.2 AlCl catalyst, catalytic activity is as low as 54 to 64 g-polymer/g-Ti, and the molecular weight of the resulting polymer is only 550 to 750. Similarly, in the case of the Pd(C.sub.6 H.sub.5 CN).sub.2 Cl.sub.2 catalyst, catalytic activity is as low as 72 g-polymer/g-Pd, and the molecular weight of the resulting polymer is about 9,000.
As a result of investigations to produce a high molecular weight norbornene-based polymer having a vinylene-type structure which could not be produced, it has been found that polymerization of a norbornene-based monomer using a catalyst comprising a combination of a specified transition metal compound and a specified organometallic compound unexpectedly provides a norbornene-based polymer having a high molecular weight which could not be obtained, and furthermore mainly having a vinylene-type structure.